In recent years, an all-solid battery in which an electrolytic solution is replaced by a solid electrolyte is attracting attention. Compared with a secondary battery using an electrolytic solution, the all-solid battery using no electrolytic solution does not cause decomposition, etc., of an electrolytic solution due to overcharge of the battery and has high cycle durability and high energy density.
The inside of such an all-solid battery includes a laminate in which a positive electrode active material layer, a solid electrolyte layer and a negative electrode active material layer are stacked with each other. The production method of this laminate generally includes the following production methods:
(1) a production method by a wet-on-dry process where a negative electrode material slurry is coated on a collector layer and dried or calcined to obtain a negative electrode active material layer and a solid electrolyte slurry is coated on the negative electrode active material layer and dried or calcined to obtain a solid electrolyte layer;
(2) a production method by a wet-on-wet process where a negative electrode active material slurry is coated to form a negative electrode active material slurry layer, a solid electrolyte slurry is coated thereon to form a solid electrolyte slurry layer, and these layers are dried or calcined to obtain a negative electrode active material layer and a solid electrolyte layer; and
(3) a production method by a lamination pressing process where a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer are individually dried or calcined and stacked, and the laminate then is pressed.
The thus-obtained laminate for a battery may be subject to deformation by processing such as cutting, deformation due to repetition of charge and discharge, or partial breakage by vibration, etc., during use, and the positive electrode active material layer and thereby the negative electrode active material layer could contact with each other to cause a short-circuit. Accordingly, the shape, structure, etc., of the laminate for a battery that can prevent a short-circuit, and the production method thereof has been studied.
Specifically, in the production method of an all-solid battery of Japanese Unexamined Patent Publication No. 2015-008073, the positive electrode and the negative electrode are made to differ in the size of the stacking surface in an attempt to avoid the short-circuiting of the battery. The production method of an all-solid battery of Japanese Unexamined Patent Publication No. 2015-008073 includes pressing a negative electrode having a negative electrode active material layer and a first solid electrolyte layer, thereafter, cutting the edge part of the negative electrode, pressing a positive electrode having a positive electrode active material layer and a second solid electrolyte layer, thereafter, cutting the edge part of the positive electrode, stacking the negative electrode and positive electrode in such a way as to contact the first solid electrolyte layer side and the second solid electrolyte layer side respectively to obtain a laminate for the battery, and heat-pressing the laminate. In the production method of an all-solid battery of Japanese Unexamined Patent Publication No. 2015-008073, a technique of creating a difference in the size of stacking surfaces between the positive electrode and the negative electrode in the process of cutting the edge parts thereof is disclosed.
The production method of an all-solid secondary battery of Japanese Unexamined Patent Publication No. 2001-015153 includes providing, on a collector layer, a laminate for a battery in which a positive electrode active material layer, a solid electrolyte layer and a negative electrode active material layer are stacked with each other, and cutting the laminate on the collector layer by laser ablation, etc. In the production method of an all-solid secondary battery of Japanese Unexamined Patent Publication No. 2001-015153, a technique of processing the laminate for a battery by irradiating a laser to the side opposite the collector layer of the laminate and, when the laser reaches aluminum as the collector layer, the laser is reflected by the collector layer, is disclosed.
With respect to the production method of a transparent electrode substrate, the production method of Japanese Unexamined Patent Publication No. 2010-129403 includes depositing a release layer on a transparent substrate, depositing a transparent electrode layer on the release layer, and irradiating the release layer with laser light to partially vaporize the release layer and, at the same time, selectively removing the transparent electrode layer together with the release layer, thereby patterning the transparent electrode layer. In the production method of a transparent electrode substrate of Japanese Unexamined Patent Publication No. 2010-129403, a technique of making the light absorption coefficient of the transparent electrode layer for laser light at a predetermined wavelength lower than the light absorption coefficient of the release layer, thereby allowing part of the laser to be transmitted through the transparent electrode layer to selectively vaporize the release layer, is disclosed.